Slipper sealing means for a dual acting pump



March 19, 1963 G. H. DRUTCHAS ETAL I SLIPPER SEALING MEANS FOR A DUALACTING PUMP 5 Sheets-Sheet 1 Filed May 9, 1960 March 19, 1963 G. H.DRUTCHAS ETAL 3,081,706

SLIPPER SEALING MEANS FOR A DUAL ACTING PUMP Filed May 9, 1960 3Sheets-Sheet 2 g 4-4; 47 f? 4 A1 a M Hff /5 March 19, 1963 G. H.DRUTCHAS ETAL 3,081,706

SLIPPER SEALING MEANS FOR A DUAL ACTING PUMP Filed May 9, 1960 3Sheets-Sheet 3 Sol/RC5 I 3 r 5 22%:

.n'w I N A 1r I S E 1? V0 I 54' 4cru4 T01? 42 Eran-fans Gilberf h-Drufchas Huber) M. C/ar/r 3,081,706 SUPPER SEALING MEANS FUR A DUALACTING PUMP Gilbert H. Drutchas, Detroit, and Hubert M. Clark,

Bloomfield Township, flaldand County, Mich, assiguors to Thompson RamoWooldridge Inc., Cleveland, Uhio,

a corporation of Ohio Filed May 9, 1960, Ser. No. 27,622 13 Claims. (Cl.103-4) This disclosure constitues a continuation-in-part of ourcopending application Serial No. 814,516, filed May 20, 1959, thedisclosure of which has now been combined herewith. Said applicationSerial No. 814,516 has been abandoned but the disclosure thereof has notbeen abandoned and has been combined with the instant application.

This invention relates generally to slipper piston pumps and moreparticularly to a slipper-type pump wherein a sealing pin operable as abalancing check valve balances difierences of pressure peaks between thecircuits to assure a more uniform noise level.

It is an object of the present invention to provide a slipper-type pumpwherein a sealing pin is utilized in such a manner as to aiford the useof a lower ratio of vane section output to slipper piston output withoutappreciably reducing the physical strength of the rotor.

Another object of the present invention is to provide a sealing pinarrangement for a slipper-type pump wherein the sealing pin is energizedby the action of centrifugal force to eifect an etlicient seal betweenthe slipper and the adjoining rotor Wall.

Yet another object of the present invention is to provide an optimum pinaction angle for a pin-sealed slippertype pump wherein the resistance tothe self-energized sealing force will be minimized.

Yet another object of the present invention is to provide a pumpconstruction having two separate pumping circuits and utilizing adirectional check valve means between circuits.

A still further object of the present invention is to provide a checkvalve means for a double circuit type pump wherein the check valve meansincludes a sealing pin interposed between the adjoining side Walls of arotor notch and a slipper-type pumping element.

Another object of the present invention is to provide a check valveaction in a two-circuit-type pump which is dynamically responsive enoughto balance differences of pressure peaks between the circuits, thusassuring a more uniform pump noise level between sections.

Many other features, advantages and additional objects of the presentinvention will become manifest to those versed in the art upon makingreference to the detailed description which follows and the accompanyingsheets of drawings in which a preferred structural embodiment of a pumpincorporating the principles of the present invention is shown by way ofillustrative example.

On the drawings:

FIGURE 1 is an end elevational view of a pump incorporating theprinciples of the present invention and having portions thereof brokenaway to illustrate the general operating environment of a rotor andslipper embodying the inventive improvements disclosed;

FIGURE 2 is a cross-sectional view taken generally on line 11-11 ofFIGURE 1;

FIGURE 3 is a reduced elevational view of the rotor incorporated in thepump of FIGURES 1 and 2;

FIGURE 4 is an enlarged side elevational view of a slipper provided inaccordance with the principles of the present invention;

FIGURE 5 is a plan view of the slipper of FIGURE 4;

FIGURE 6 is a fragmentary cross-sectional view show- 3,081,7dd PatentedMar. 19, 1963 ing a slipper in cross-section and illustrating therelationship thereof to the rotor of the present invention; and

FIGURE 7 is a fragmentary view showing details of construction of therotor notch provided in accordance with the principles of the presentinvention.

FIGURE 8 is a cross-sectional view of a slipper-type pump incorporatingthe principles of the present invention;

FIGURE 9 is a cross-sectional view with parts shown in elevation takengenerally on line IXIX of FIGURE 8; and

FIGURE 10 is a fragmentary cross-sectional view illustrating a modifiedembodiment of a slipper-type pumping element construction in accordancewith the principles of the present invention.

As shown on the drawings:

The pump of the present invention is shown generally at it and comprisesa casing 11 having a first housing part 12 connected to a second housingpart 13 by a plurality of fasteners 14.

The housing part 12 has formed therein a bore 16 counterbored as at 17to form a pumping chamber having an outer cylindrical bore wall 18 and aradial side wall 19.

The housing part 13 provides on the other side of the pumping chamber 17a radial end wall 2d.

A rotor 21 is provided which has an outer cylindrical peripheral surface22 of lesser diameter than the bore wall 18 and the rotor 21 isrotatable within the pumping chamber 17 on a rotational axis which isoifset from the axis of the pumping chamber 18, thereby to form acrescent-shaped working chamber in the pumping chamber 18 which isindicated at 23 in FIGURE 1.

As shown in FIGURE 3, the rotor is an essentially cylindrical elementhaving formed therein a plurality of peripheral notches 24, theexemplary form of the invention herein disclosed utilizing a rotor 21having seven notches formed in the periphery thereof. Each notch isshown in specific detail in FIGURE 7. It will be noted the notch 24 hasa first side wall 26 and spaced therefrom in generally parallel relationtherewith is a second side wall 27. A bottom wall 28 is provided whichmerges with the side wall 27 via an angularly inclined portion 29, Whilethe bottom wall 28 merges with the side wall 26 via anirregularly-shaped portion 30 forming a stop shoulder.

A slipper indicated generally at 31 is provided for each notch 24. Eachslipper has a curved outer sealing surface 32 which is contoured to beseverally complementary to the bore wall 18 and which will, therefore,engage the bore wall with a surface contact. The slipper sealing surfacebeing of a slightly smaller radius than the bore wall, the contactbetween the surfaces will be in eifect, a land contact.

At one side of the slipper 31, there is provided an end wall 33 whichcurves generally outwardly of the sealing surface 32 and terminates inan inwardly directed wall 34. As shown in FIGURE 6, the wall 33 of theslipper 31 is adapted to sealingly engage the adjoining side Wall 26 ofthe notch 24 in the rotor 21.

The inwardly directed wall 34 terminates in a shoulder 36 which isdisposed between the wall 34 and a flat end wall 37 in which is formed arecess 38 for bottoming one end of a coil spring 35, the other end ofwhich is bottomed against the bottom wall 28 of the notch 24, thereby tocontinuously bias the slipper 31 generally outwardly of the notch 24-.

At the opposite side of the slipper 31, there is formed a pair of wingsections 39 and 40, each of which providing a curved overhangingretaining surface 41 forming the upper boundaries of a recess 42 whichextends inwardly of a side wall 43 on the slipper 31.

Spaced from the retaining surface 41 and on the opposite side of therecess 42 from the retaining surface 41 is a surface 44 which isinclined generally outwardly, thereby to form what will be referred tohereinafter as a pin action surface 44.

Between the wing portions 39 and 40, there is formed an enlarged recessprovided by an inwardly directed wall 46 which includes an oifsetportion 47 intersecting the wall 37.

The slipper 31 is also provided with flat parallel ends shown at 48 and49, respectively.

As will be noted upon inspecting FIGURE 6, the spacing dimension betweenthe wall 33 and the wall 43 on the slipper 31 is somewhat less than thespacing dimension between the wall 26 and the wall 27 of the notch 24.

There is thus provided in accordance with the principles of the presentinvention, a sealing means between the wall 43 and the wall 27. Byvirtue of such sealing means, the pump is particularly adapted todevelop a dual pumping action characterized by the provision of innerand outer pumping circuits. Thus, the pump is suitably ported with inletand outlet ports communicating with the working chamber 23 so that afirst pumping circuit will be established outwardly of the sealing meansbetween the Wall 43 and the wall 27. Additionally, the pump is ported,for example, by means of side wall ports shown at 56 in FIGURE 2 adaptedto communicate with the inner portions of the notches 24, thereby toestablish a second pumping circuit inwardly of the sealing means.

In this particular form of the invention, the sealing means takes theform of a cylindrical pin 51 having a length corresponding to thespacing dimension between the ends 48 and '49 of the slipper 31 andhaving a peripheral sealing surface 52 which is adapted to engageagainst the wall 2'7 and against the slipper 31, thereby to sealinglyisolate the inner and outer pumping circuits of the pump 10. It will beunderstood that the term sealing pin as employed herein refers to asealing means of any suitable shape and particularly other shapes of pinsections.

In accordance with the principles of the present invention, the sealingpin 51 is positioned in the recess 42 extending inwardly of the sidewall 43 and in the slipper 31. By using this arrangement instead ofplacing thepin in a recess formed within the wall 27 of the notch 24, itis possible to use a lower ratio of vane section output to slipperpiston output without appreciably reducing the physical strength of therotor, particularly in the critical strength section shown at 53 inFIGURE 3.

The sealing pin 51 is energized by the action of centrifugal force uponrotation of the rotor 21, thereby effecting a good sealing actionbetween the slipper 31 and the wall 2'7 of the rotor 21.

In order to enhance the self-energizing sealing force, the presentinvention contemplates the provision on the slipper 31 of the actionsurface 44 engageable with the peripheral surface 52 of the pin 51.Although the pin action angle need not be selected with criticalanalysis, it is contemplated by the present invention that the pinaction angle be adjusted to give the least or minimal resistance to theself-energizing sealing force. Thus, in the illustrative embodimentherein disclosed, the pin action angle, as indicated on FIGURE 6 at 54is approximately 30.

In a dual acting pump of the type herein disclosed, it is possible thatthe pressure in the outer pumping circuit might be greater than thepressure within the inner pumping circuit. If such differential exists,it is possible that the pin 51 would be unrestrained by the side walls43 and 27, which lack of restraint might result in the pin beingphysically displaced out of proper position.

In accordance with the principles of the present invention, the pinmeans 51 is particularly adapted to act as a one directional checkvalve. This advantageous function is developed by forming on the wingsections 39 and 4d the restraining surfaces 41 which in part overlie therecess 42 cut away into the side wall 43 of the slipper 31 and therebyserve to confine the pin 51 within the recess. Thus, the pin 51 normallyseals in the direction of the outer pumping circuit and will continue todo so as long as the inner pumping circuit pressure is greater than thepressure in the outer pumping circuit. With the reverse true, however,the outer pumping circuit pressure will force the pin 51 inwardlyagainst the restraining surfaces 41, thereby insuring that equalpressure will exist in both pumping circuits.

Moreover, by utilization of the pin 51 as a check valve an improveddegree of noise control can be achieved. It has been determined thatvehicular pump noise is closely related to pressure peaking. The checkvalve action of the sealing pin 51 is dynamically responsive enough tobalance differences of pressure peaks between the pumping circuits, thusassuring a more uniform noise level between the sections. The stop 34)positioned in register with the pin 51 prevents overtravel of the sealpin '51 inwardly.

The pump shown in FIGURES 8, 9 and 10 is indicated generally at 10 andcomprises a casing 11 forming a housing for the pump in which is formedan inlet 12 and an outlet 13'.

A pumping chamber 14 is formed in the housing 11' and includes agenerally cylindrical bore formed by a bore wall 16 recessed on one sideof the pump to provide an inlet recess 17 and recessed on the oppositeside of the pump to provide an outlet recess 18.

The casing forming the housing 11 is closed by a cover member 19'retained in firm assembly with the housing 11 by a plurality offasteners indicated at 20.

In order to develop a pumping action between the inlet 12 and the outlet13', there is provided a generally cylindrical rotor 21' having an outerperipheral surface 22 which is of a diameter less than the insidediameter of the bore wall in.

The rotor 21' is particularly characterized by the formation in theperipheral surface 22' of a plurality of circumferentially spacednotches, recesses, or slots herein indicated at 23 and which may berectangular in crosssectional configuration as prescribed by spacedapart side walls 24 and 26 extending radially inwardly fromthe outerperipheral surface 22 and terminating in a bottom wall 27'.

Each slot 23' receives a slipper-type pumping element indicatedgenerally at 28' which is free to move radially and to rock angularly.As shown in FIGURES 8, 9 and 10, each slipper-type pumping element 28 isof a generally U-shaped configuration in cross-sectional configurationincluding a bight portion 29 forming a surface contact area 30' forengaging against the bore wall 16. Each slipper-type pumping elementfurther includes spaced leg portions indicated at 31' and 32,respectively, the side wall of the leg 31 being indicated at 33' and theside wall of the leg 32 being indicated at 34'. The side walls 33 and 34diverge somewhat in an outward direction and terminate in end portionsadapted to slidably engage against the adjoining walls 24 and 26' of acorresponding s 0t 23.

Bottomed against the inside of the bight portion 29, as indicated at 36,is a coil spring 37' having its opposite end engaged against anadjoining bottom wall 27 of a corresponding slot 23'. Thus, theslipper-type pumping element 28' is preloaded in radially outwardlyextending direction.

In order to rotate the rotor 21' on a rotational axis offset from thecenter axis of the pumping chamber 14', there is provided a boss 38formed in the housing 11 through which extends a shaft passage 39carrying a pair of spaced bearings 4t) and 41' which, in turn, rotatablysupport a shaft indicated at 42. The shaft 42' has connected therewith acoupling member 43' splined as at 44' to the rotor 21.

The rotational axis of the shaft 42' is eccentrically offset withrespect to the center axis of the bore wall 16', thereby providingbetween the housing 11 and the rotor 21 a sealing area 46 extendingbetween the inlet and the outlet 12 and 13 and further forming acrescent-shaped working area 47' which extends from one side of the pumpadjacent the inlet 12 and its corresponding inlet recess 17' and theoutlet 13' and its corresponding outlet recess 18 on the other side ofthe pump. Thus, when the rotor 21 is rotatably driven by the shaft 42,the slipper-type pumping elements 28 which are continuously biased intoengagement with the bore wall 16, will follow the contour prescribed bythe bore wall 16' and the rotation of the rotor 21 in the eccentrichousing bore 14' causes an expansion and contraction of the volumebetween adjacent slipper-type pumping elements 28' as the elements 28traverse the crescent-shaped working area 47'. Accordingly, a pumpingaction will be developed between the inlet 12 and the outlet 13'.

In accordance with the principles of the present invention, the housing11' is particularly characterized by the formation therein of an arcuateinlet slot 51) on the inlet side of the pump and an arcuate outlet slot51 on the outlet side of the slot. The inlet slot 5%) and the outletslot 51 are formed to be disposed generally radially inwardly of theslipper-type pumping elements 28', but extend at least partiallyradially outwardly of the bottom wall 27 of each respective notch orslot 23.

The housing 11' further includes a passage 52' communicating the inletslot 56 with a topped opening 53 whereby the inlet 58 may be connectedto a pumping circuit indicated by legend as comprising a source of fluidpumping medium.

The housing ll further includes a passage 54' which connects the outletslot 51 to a tapped opening indicated at 56 adapted to be connected byappropriate means to a point of utilization.

As is clearly indicated in the drawings, when the notches of the rotor21 are opposite the sealing area 46 the clearance dimension between theperipheral surface 22 and the bore wall 16 are at a minimum and,accordingly, the corresponding slipper-type pumping element 23 isdepressed against the continuous biasing means provided by the coilspring 37 and the pumping element is retracted into the slot 23, therebyto minimize the volume thereof.

As the rotor 21 carries a pumping element 28' past the inlet side of thepump, the pumping element starts to move radially outwardly as the innerportions of the slot 23' come adjacent the inlet slot Sit and thevolumetric area defined between the bottom of the slot 23' and aslipper-type pumping element 28' increases.

As the pumping elements 28 are carried past the outlet side of the pump,the volumetric area again decreases. Accordingly, the rotation of therotor 21 imparts a radial in and out pumping action to the slipper-typepumping elements 28' and develop a pumping action between the inlet 50and the outlet 51.

In order to assist in developing an adequate seal between the pumpingcircuits 12, 13' and 5d, 51, the pumping elements of the presentinvention may be provided as shown in the embodiment of FIGURE In thatarrangement, a notch or slot is indicated at 2311' and one of the sidewalls such as the wall 24a is recessed as at 69, thereby to receive apin 61, herein shown as being of cylindrical configuration and of alength corresponding in length to a slipper-type pumping element shownat 28a.

The pin 61' fits in the recess so and has a portion extending outwardlyof the wall 24a into the slot 23a, thereby to engage against the sidewall 33a of the pumping element 28a. Thus, the pumping element 28a isfree to conformably engage the bore wall 16a of the housing 11a and thepumping element 28a is free to move radially in the slot 23a, as well asto rock angnllarly. However, because the opposite leg 34a of the pumpingelement 2.8a engages against the wall 26a of the slot 23a, the pin 61assists in controlling leakage between the separated pumping circuitsexisting between the inlet 12' and the outlet 13', and between theinlet. 50' and the outlet 51.

The pump of the present invention is particularly useful in atransmission application wherein one of the pumping circuits can be usedfor servo actuation and the other for an hydraulic governor. Thus, asillustrated diagrammatically herein, the inlet 12' is shown connected toa source of fluid pumping medium while the outlet 13 is shown deliveringfluid to an hydraulic governor. The other separate pumping circuit, asillustrated in FIGURE 9, indicates the inlet 50' connected to a suitablesource and the outlet 51 discharging to a servo actuator.

though minor modifications might be suggested by those versed in theart, it should be understood that we wish to embody within the scope ofthe patent warranted hereon all such modifications as reasonably andproperly come within the scope of our contribution to the art.

We claim as our invention:

1. A pump comprising a casing having a cylindrical bore wall forming apumping chamber,

a rotor rotatable on an offset axis in said pumping chamber,

means forming a peripheral axially extending recess in said rotor havinggenerally parallel side walls and a bottom wall,

a slipper in said recess having a radial outer sealing surface curved toengage the adjoining bore wall with surface contact and including firstand second side walls disposed adjacent said side walls of saidrecesses,

said first and second side walls being shaped to permit said slipper torock and to move inwardly and outwardly of said recess in followin saidbore wall,

said first side wall of said slipper engaging the adjoining side wall ofsaid recess,

means forming a sealing pin interposed between said second side wall ofsaid slipper and the other side wall of said recess,

and radially outer and inner porting means in said casing respectivelycommunicating with said pumping chamber radially outwardly of saidsealing pin to form a first pumping circuit and with said recessradially inwardly of said sealing pin to form a second pumping circuit,

a sealing pin recess in one of said side Walls receiving said sealingpin and having means of a form and inward extent such that the pin willmove inwardly away from an adjoining side wall out of sealing contact torelieve excessive pressures in the first pumping circuit and will moveoutwardly against the adjoining walls in sealing contact in response tocentrifugal force to retain pressure in the second pumping circuit.

2. A pump comprirsing a casing having a cylindrical bore wall forming apumping chamber,

a rotor rotatable on an ofiset axis in said pumping chamber,

means forming a peripheral axially extending notch in said rotor havinggenerally parallel side walls and a bottom wall,

a slipper in said notch having a radial outer sealing surface curved toengage the adjoining bore wall with surface contact and including firstand second side walls disposed adjacent said side walls of said notch,

said first and second side walls being shaped to permit said slipper torock and to move inwardly and outwardly of said notch in following saidbore wall,

said first side wall of said slipper engaging the adjoining side wall ofsaid notch,

means forming a sealing pin carried by said slipper at said side walland engageable with the adjoining side wall of said notch,

radially outer and inner porting means in said casing respectivelycommunicating with said pumping chamber radially outwardly of saidsealing pin to form a first pumping circuit and with said notch radiallyinwardly of said sealing pin to form a second pumping circuit,

said slipper side wall having a pin recess formed therein receiving saidsealing pin,

said pin recess having an action surface converging radially outwardfrom the recess towards the notch side wall,

the inward extent and form of the pin recess being such to permitmovement inwardly away from said notch side wall of the sealing pin outof sealing relation in response to excess pressures to relieve highpressures in the first pumping circuit and to permit movement outwardlyof the sealing pin against said notch side wall and said action surfacein response to centrifugal force to retain pressure in the secondpumping circuit.

3. For use in a pump of the type having inner and outer pumpingcircuits, a peripherally notched rotor, a pumping element of a width anda thickness sufficiently less than the width and depth of the notch inthe rotor so that said pumping element is free to move radially and rockangularly,

said pumping element having a side wall formed with a recess therein,

said recess having an action surface inclined generally outwardly at aconverging angle to the adjoining side wall of the rotor notch,

and a sealing means in said recess and engaging said action surface andan adjoining surface of said rotor during rotation and wedging againstsaid surfaces in response to centrifugal force to retain pressure in theinner pumping circuit and to move inwardly out of sealing relation withsaid surfaces to relieve excessive pressure in the outer pumpingcircuit.

4. In a pump of the type having inner and outer pumping units havingradially inner and outer pumping circuits,

a peripherally notched rotor,

a pumping element in said rotor of a width and a thickness sufficientlyless than the width and depth of the notch in the rotor so that saidpumping element is free to move radially and rock angularly,

said pumping element developing a pumping action in both said inner andouter circuits,

and means including said rotor forming a check valve means between saidinner and outer circuits to balance the circuits and to balancedifferences of pressure peaks in said circuits,

said check valve means including a movable check valve element and arecess between the adjoining walls of said pumping element and thenotched rotor and further including means forming an action surfaceconverging radially outwardly from the recess, whereby said movablevalve element will be moved inwardly out of sealing relation with saidaction surface and an adjoining surface of said rotor in response tohigh pressures in the outer circuit and will move outwardly against saidsurfaces in sealing relation in response to centrifugal force to retainpressure in the inner circuit.

5. In a pump of the type having inner and outer pumping units havinginner and outer pumping circuits with a peripherally notched rotor,

a pumping element in said rotor of a width and a thickness suificiently'less than the width and depth of the notch in the rotor so that saidpumping element is free to move radially and rock angularly fordeveloping a pumping action in both the inner and outer circuits andmeans including said rotor forming a check valve means between saidinner and outer circuits to accommodate flow from the outer to the innercircuit when the pressure in the outer circuit exceeds the sealingpressure on the check valve means thereby to balance the circuits and tobalance differences of pressure peaks in said circuits, said check valvemeans comprising means forming a side wall in said pumping elementhaving an outwardly inclined action surface converging towards theadjoining notch side wall and a cylindrical pin movable toward and awayfrom sealing engagement with said action surface and with said notchside wall in response to centrifugal force and excess pressure in theouter circuit, respectively, said side wall including inwardly inclinedportions spaced from said action surface and together therewith forminga confining recess for said pin.

6'. In combination,

a pump rotor having a peripheral notch including side walls outwardly ofthe rotor axis,

a slipper in said notch of a width and a thickness sufficiently lessthan the width and depth of the notch in the rotor so that said slipperis free to move radially and rock angularly,

and a sealing pin confined between said slipper and one of said sidewalls,

means forming sealing surfaces radially outwardly of said pin on saidrotor and on said slipper,

said sealing pin being energized by the action of centrifugal force uponrotation of said rotor to engage said surfaces and thereby produce aself-energizing sealing force between the slipper and the rotor,

means forming a sealing pin recess between said slipper and said one ofsaid walls,

said sealing surface on said slipper being disposed in angularlyinclined relation to the adjoining notch side wall and extendingoutwardly from said recess to accommodate movement of said pin inwardlyinto said recess out of sealing relation with said surfaces in responseto excess pressures to relieve high pressures outwardly of the pin.

7. For use in a slipper-type pump,

a casing having a bore forming a pumping chamber,

a peripherally notched rotor,

a slipper having a curved outer radial sealing surface for effectingsurface sealing engagement with an adjoining bore wall of a pumpingchamber,

said slipper being of a width and a thickness sufficiently less than thewidth and depth of the notch in the rotor so that said slipper is freeto move radially and rock angularly,

a first side wall on said slipper for engaging the adjoining side of arotor notch.

and a second side wall on said slipper recessed to form an outwardlyinclined surface and having clearance with the adjoining rotor sidewall,

and a cylindrical sealing pin energized by the action of centrifugalforce upon rotation to seal against said inclined surface and theadjoining rotor side wall of the notch,

said second side wall having wing portions at opposite sides thereofformed with curved recesses complementary to the shape of the pin,thereby to retain the pin for a check valve action between inner andouter pumping circuits in the pump.

8. A slipper-type pump comprising a housing having a working chamberformed with an inlet and an outlet,

a rotor having a notch formed therein with radially extending side wallsand being rotatable on an axis eccentrically offset in said chamber,

the inward extent and form of said recess being such to permit radiallyinward movement of said pin out of sealing relation with either or bothsaid pumping element and said rotor in response to excessive pressuresradially outwardly of the sealing pin and moving radially outwardly intosealing engagement with said pumping element and with the adjoiningportions of said rotor in response to centrifugal force. 11. In a pumpas defined in claim 10, a coil spring wardly, said housing having meansforming a second inlet and a separate second outlet at the respectiveinlet and bottomed against said rotor and said slot and engaging againstthe inside of said bight portion to load said slippertype pumpingelement radially outwardly.

outlet sides of the pump and communicating with the innermost portionsof said notch,

said slipper being radially reciprocable in said notch and completing astroke between said second inlet and said second outlet to develop asecond pumping action,

and sealing means interposed between the side Walls of said slipper andsaid notch comprising a recess formed in one of said side wallsproviding an action suface converging radially outwardly towards theother of said side walls adjoining said one side wall,

said pin moving outwardly into sealing engagement with said surface andthe adjoining rotor Wall in response to centrifugal force, the inwardextent and form of said recess being such to permit movement of thesealing means inwardly out of sealing contact with either or both saidsurface and said adjoining rotor wall to relieve pressures in the outercircuit higher than the pressures in the inner circuit,

thereby to balance differences of pressure peaks in said circuits.

9. In a pump,

a rotor having a rectangularly shaped peripheral slot,

a slipper-type pumping element in said slot,

said slot and said pumping element having side walls of correspondingwidth and depth dimensions proportioned so that said pumping element isfree to move radially and to rock angularly while following the contourof an adjoining pumping chamber Wall, said rotor having a longitudinallyextending recess formed in the walls of said slot,

and a sealing pin in said recess and extending into said slot to engagethe adjoining portion of said slipper-type pumping element to assist insealing the pumping element in the rotor,

the inward extent and form of said recess being such to permit radiallyinward movement of said pin out of sealing relation with either or bothsaid pumping element and said rotor in response to excessive pressuresradially outwardly of the sealing pin and moving radially outwardly intosealing engagement with said pumping element and with the adjoiningportions of said rotor in response to centrifugal force.

18. In a pump,

a rotor having a rectangular slot in the periphery thereof,

a slipper-type pumping element in said slot comprising a U-shaped memberhaving a bight portion extending outwardly of said slot to engaginglyfollow the contour of an adjoining pumping chamber wall,

said U-shaped member further including leg portions spade apartsufficiently less than the width of the slot and the corresponding depthdimension of the slot and the pumping element being such that saidpumping element is free to move radially and to rock angularly,

and a sealing pin corresponding in length with said pumping element andinterposed between one of said leg portions of said pumping element andan adjoining wall of said slot to assist in sealing the pumping elementin the rotor,

said wall having a pin recess formed therein,

12. In a hydraulic transmission,

a slipper pump having a housing formed with separate inner and outerinlets and outlets,

a peripherally notched rotor, slipper means in the notch of said rotorof a Width and thickness suficiently less than the Width and depth ofthe notch that the slipper means is free to move radially and to rockangularly while following the contour of the adjoining housing wall.

means forming a pumping chamber between said outer inlet and outlet,

whereby fiuid is pumped therebetween upon rotation of said rotor in saidhousing,

means in said housing communicating said inner inlet and outlet with theportions of said peripherally notched rotor radially inwardly of saidslipper means,

whereby fluid is pumped therebetween by the radial reciprocation of saidslipper means in said rotor,

servo actuating means connected to one of said outlets, and hydraulicgovernor means connected to the other of said outlets,

and sealing means interposed between said slipper means and an adjoiningside wall of said notch,

said sealing means having a recess and a pin received therein, saidrecess being of a form and inward extent to permit movement of the pinout of sealing relation with said adjoining side wall of said notch andwith said slipper means in response to excessive pressures radiallyoutwardly of the pin,

said pin being movable radially outwardly into sealing engagement withsaid adjoining side wall of said notch and with said slipper means inresponse to centrifugal force to retain pressure radially inwardly ofthe slipper means.

13. In a pump,

a casing having a pumping chamber formed with a wall,

a rotor having a rectangular slot in the periphery thereof,

a slipper-type pumping element in said slot comprising a U-shaped memberhaving a bight portion extending outwardly of said slot to engaginglyfollow the contour of the adjoining pumping chamber wall,

said U-shaped member further including leg pontions spaced apartsufliciently less than the width of the slot and the corresponding depthdimension of the slot and the pumping element being such that saidpumping element is free to move radially and to rock angularly,

a pin correspondingly in length with said pumping element and interposedbetween one of said leg portions of said pumping element and anadjoining wall of said slot,

and means forming first and second pumping circuits disposed,respectively, inwardly and outwardly of said pin,

whereby said pumping element will develop a dual pumping action,

one of said legs of said U-shaped member having a recess formed therein,

an action surface coverging radially outwardly from the recess towardsthe adjoining side wall of the slot,

the inward extent of the recess being such to permit movement of the pinout of sealing relation with said adjoining wall of said slot and withsaid one of said legs of said U-shaped member in response to excessivepressures outwardly of the pin,

said pin being movable outwardly into sealing engagement with saidadjoining Wall of said slot and with said one of said legs of saidU-shaped member in response to centrifugal force.

1,495,526 Phillips May 27, 1924 Livermore Mar. 31, 1942 Livermore Nov.2, 1943 Links Sept. 14, 1954 Roth Oct. 21, 1958 Deschamps Sept. 13, 1960Livermore et a1 Nov. 21, 1961 FOREIGN PATENTS Italy May 15, 1939 GermanySept. 24, 1936 France Nov. 3, 1954

1. A PUMP COMPRISING A CASING HAVING A CYLINDRICAL BORE WALL FORMING APUMPING CHAMBER, A ROTOR ROTATABLE ON AN OFFSET AXIS IN SAID PUMPINGCHAMBER, MEANS FORMING A PERIPHERAL AXIALLY EXTENDING RECESS IN SAIDROTOR HAVING GENERALLY PARALLEL SIDE WALLS AND A BOTTOM WALL, A SLIPPERIN SAID RECESS HAVING A RADIAL OUTER SEALING SURFACE CURVED TO ENGAGETHE ADJOINING BORE WALL WITH SURFACE CONTACT AND INCLUDING FIRST ANDSECOND SIDE WALLS DISPOSED ADJACENT SAID SIDE WALLS OF SAID RECESSES,SAID FIRST AND SECOND SIDE WALLS BEING SHAPED TO PERMIT SAID SLIPPER TOROCK AND TO MOVE INWARDLY AND OUTWARDLY OF SAID RECESS IN FOLLOWING SAIDBORE WALL, SAID FIRST SIDE WALL OF SAID SLIPPER ENGAGING THE ADJOININGSIDE WALL OF SAID RECESS, MEANS FORMING A SEALING PIN INTERPOSED BETWEENSAID SECOND SIDE WALL OF SAID SLIPPER AND THE OTHER SIDE WALL OF SAIDRECESS, AND RADIALLY OUTER AND INNER PORTING MEANS IN SAID CASINGRESPECTIVELY COMMUNICATING WITH SAID PUMPING CHAMBER RADIALLY OUTWARDLYOF SAID SEALING PIN TO FORM A FIRST PUMPING CIRCUIT AND WITH SAID RECESSRADIALLY INWARDLY OF SAID SEALING PIN TO FORM A SECOND PUMPING CIRCUIT,A SEALING PIN RECESS IN ONE OF SAID SIDE WALLS RECEIVING SAID SEALINGPIN AND HAVING MEANS OF A FORM AND INWARD EXTENT SUCH THAT THE PIN WILLMOVE INWARDLY AWAY FROM AN ADJOINING SIDE WALL OUT OF SEALING CONTACT TORELIEVE EXCESSIVE PRESSURES IN THE FIRST PUMPING CIRCUIT AND WILL MOVEOUTWARDLY AGAINST THE ADJOINING WALLS IN SEALING CONTACT IN RESPONSE TOCENTRIFUGAL FORCE TO RETAIN PRESSURE IN THE SECOND PUMPING CIRCUIT.